I would like to speak with the manager.
'Responsabile' — res-pon-SA-bi-le. Five syllables.
Use as an escalation when the shop assistant cannot or will not resolve your issue. Say it calmly — it is not an aggressive phrase but signals you are serious.
'Responsabile' means the person in charge or manager. 'Vorrei' (conditional of volere) keeps the tone polite. In Italy, direct confrontation with a junior employee rarely works — staff are more empowered to help when the matter is elevated to a supervisor.
C'è qualcuno che può aiutarmi?
Is there someone who can help me?
Softer escalation.
Posso parlare con il direttore?
Can I speak with the director?
'Direttore' is more senior than 'responsabile'.
Chi devo contattare per questo problema?
Who should I contact about this problem?
Opens the door to alternative channels.
Italian shop managers have significant discretion in Italy. They can approve exceptions to policy that junior staff cannot. Staying calm and polite with the manager is almost always more effective than showing frustration.